It is known to provide micromechanical structures on the surface of semiconductor components, for example of silicon wafers containing integrated circuits (ICs). These may be freely moving sensor elements constructed as capacitive acceleration sensors which comprise a resiliently suspended seismic mass and also a comb-structure system for capacitively evaluating the deflections of the seismic mass associated with acceleration.
To form such components with micromechanical structure, the conventional methods of surface micromechanics utilize, for example, sacrificial layers integrated in the wafer structure and active silicon layers situated on top thereof and composed, for example, of polysilicon on top of silicon oxide islands, with the result that a massive intervention has to be made in the IC process.
According to a further known production method, these sensor elements are formed with the aid of the LIGA technology in electrodeposited metal layers. In the LIGA method, high X-ray resist structures produced by synchrotron exposure are formed by electroplating, and a first mold is first obtained therefrom. The mold is then used to imprint under high pressure polymer layers which are provided on wafers and which consequently yield a female mold which is then filled by electroplating. The polymer mold is then destroyed so that the sensor element is laid bare. A disadvantage of this process is that a synchrotron exposure can be carried out only with high and consequently expensive effort using additional synchrotron installations which are not a common manufacturing feature of semiconductor component production. As a result of the high molding pressures during the molding of the female structures, there is furthermore the risk of destroying the wafer, the mold or electronic circuits integrated in the wafer. During the molding of the sensor elements, a precise alignment with the circuits contained on the wafers also presents problems. As a result of wear of the mold, it is necessary to produce a plurality of daughter modes by remolding before the actual production of the sensor elements can take place.
Hitherto it has not yet been possible in practice to demonstrate the serviceability of the process as a whole. The molding on an IC wafer is always a dangerous intervention in the IC process.